Dementia occurs as a result of physical changes in the structure of the brain. These changes can affect memory, thinking, behaviour, personality and emotion. Because dementia is a progressive syndrome, symptoms will gradually worsen. The most common form of dementia is Alzheimer’s disease, although there are several other forms. No single factor has been identified as a cause for dementia or Alzheimer’s disease. It is likely that a combination of factors, including age, genetic inheritance and environment are responsible. There are over 48,000 people with dementia in New Zealand. Alzheimers New Zealand works with people with dementia, their family/whanau, friends and community. We estimate around 300,000 New Zealanders are affected by dementia. People of all ages, ethnicities and intellectual ability can get dementia. While it is more common in people over the age of 65, it can also affect younger people.

Dementia usually causes difficulties with some of the following ;
  • remembering
  • thinking and planning
  • making decisions
  • motivation/initiation
  • looking after yourself
  • expressing thoughts
  • understanding what others are saying
  • finding your way around
  • managing finances
Dementia is not ;
  • part of normal ageing
  • contagious
  • something to be ashamed of or hidden away
  • something that you have to face alone

Common Forms of Dementia

Alzheimer’s disease

Alzheimer’s disease is the most common cause of dementia (50-70%). As the disease progresses, physical changes occur in the structure of the brain. Brain cells die and the brain shrinks, especially in the inner parts of the temporal lobes. Plaques and tangles form in brain tissue and disrupt messages between brain cells, preventing the brain from working efficiently. People with Alzheimer’s disease experience a gradual decline in their ability to remember, understand, communicate and reason. Some medications are available, which may mask the progression of Alzheimer’s disease in the early stages.

Huntington’s disease

Huntington’s disease is a progressive hereditary disease, which most often becomes apparent in adults in their thirties. Dementia can occur at any stage in the illness. Symptoms of dementia associated with Huntington’s disease include loss of short term memory and loss of planning and organisational skills, lack of insight into the condition, lack of concern for other people’s needs, obsessive behaviour and reluctance to accept help. This form of dementia differs from Alzheimer’s disease in that those affected continue to recognise people and places.

Parkinson’s disease

Parkinson’s disease is a progressive neurological disease affecting movement. While people with Parkinson’s disease have a higher risk of developing dementia than those without Parkinson’s disease, the majority will remain unaffected. How dementia occurs in Parkinson’s disease is not yet understood. It may be that the Lewy bodies, which occur in nerve cells in the brains of people with Parkinson’s act the same way as they do in people with dementia with Lewy bodies. Also, side effects of certain drugs for Parkinson’s may exacerbate symptoms of dementia. The most common symptoms of dementia associated with Parkinson’s disease are memory loss, the loss of ability to reason and to carry out normal everyday tasks, obsession and loss of emotional control. Visual hallucinations may occur and symptoms often fluctuate.

Lewy bodies

Dementia with Lewy bodies (DLB) is similar to Alzheimer’s disease in that it is caused by the degeneration and death of nerve cells in the brain. Lewy bodies are tiny protein deposits found in nerve cells and their presence disrupts the brain’s normal functioning, interrupting the action of important chemical messengers. Lewy bodies are also found in the brains of people with Parkinson’s disease. Researchers do not yet fully understand why Lewy bodies occur in the brain. People with DLB experience memory loss, confusion regarding time and whereabouts, communication difficulties, slowness, muscle stiffness, trembling of the limbs, a tendency to shuffle when walking, loss of facial expression and changes in strength and tone of voice characteristic of Parkinson’s disease. Symptoms of DLB include fluctuation, stiffness and trembling, a fluctuating ability to complete tasks from hour to hour, even from minute to minute as well as fainting, falling or unexplained turns and visual hallucinations. DLB affects men more than women and is more prevalent in people over the age of 65. An accurate diagnosis is important because people with DLB have reacted badly to neuroleptic drugs (strong tranquillisers), which are often prescribed to people with dementia. There is currently no cure for DLB. Some people may benefit from anti-Parkinson’s disease drugs but these may worsen hallucinations and confusion.

Vascular dementia

Vascular dementia (also called multi-infarct dementia), is the second most common form of dementia (20-30%). It is most commonly caused by multiple strokes and, occasionally, by a single stroke. Stroke occurs when blood flow in the brain is blocked by a blood clot in an artery or when an artery bursts. When this happens, brain cells are deprived of oxygen and die. People who have a large stroke will experience difficulties such as paralysis on one side of the body, speech and language problems or difficulties with coordination and movement. Some small strokes may just cause a ‘funny turn’ or not be noticed at all. However, each stroke is contributing to a build-up of damage to the brain, which can cause dementia. Smokers, people with high blood pressure, high level of fat in their blood or people with diabetes have more of a risk of developing vascular disease. Symptoms of vascular dementia are very similar to Alzheimer’s disease. However, distinguishing features include neurological symptoms including weakness, clumsiness or altered sensation in the limbs or face. Some of the abilities lost in people with Alzheimer’s disease may remain relatively unaffected in people with vascular dementia, since the condition affects the brain in a patchy fashion. Symptoms can remain steady for a while and then suddenly decline. People with vascular dementia may understand what is happening to them, more so than those with other forms of dementia, which can make them prone to depression. Vascular dementia is diagnosed by looking at the way the condition began and how it has progressed, together with evidence of stroke(s) or impaired blood supply on a brain scan. It is common to have both vascular dementia and Alzheimer’s disease.*

More Information

(*Alzheimer’s New Zealand)